RFR: 8080746: Refactor oop iteration macros to be more general

[Stefan Johansson]

Hi,

Please review this change to generalize the oop iteration macros:
https://bugs.openjdk.java.net/browse/JDK-8080746

Webrev:
http://cr.openjdk.java.net/~sjohanss/8080746/hotspot.00/

Summary:
The macros for the oop_oop_iterate functions were defined for all *Klass 
types even though they were very similar. This change extracts and 
generalizes the macros to klass.hpp and arrayKlass.hpp.

For the arrays the *_OOP_OOP_ITERATE_BACKWARDS_* macros is now called 
OOP_OOP_ITERATE_NO_BACKWARDS_* to reflect that for arrays we currently 
don't have a reverse implementation.

Thanks,
Stefan